Fix invalid enum base types being generated in C# source (#1899)

* Rename `CheckFlagEnumsPass` to `CheckEnumsPass`

* Fix invalid enum base types being generated in C# source

* Add enum base type validation tests

Author: duckdoom5

src/Generator.Tests/CppSharp.Generator.Tests.csproj

@@ -1,8 +1,8 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <ItemGroup>
-    <None Include="..\..\tests\Native\AST.h" LinkBase="tests\Native" />
-    <None Include="..\..\tests\Native\ASTExtensions.h" LinkBase="tests\Native" />
-    <None Include="..\..\tests\Native\Passes.h" LinkBase="tests\Native" />
+    <None Include="..\..\tests\dotnet\Native\AST.h" LinkBase="tests\Native" />
+    <None Include="..\..\tests\dotnet\Native\ASTExtensions.h" LinkBase="tests\Native" />
+    <None Include="..\..\tests\dotnet\Native\Passes.h" LinkBase="tests\Native" />
   </ItemGroup>
   <ItemGroup>
     <ProjectReference Include="..\Generator\CppSharp.Generator.csproj" />

src/Generator.Tests/Passes/TestPasses.cs

@@ -39,19 +39,31 @@ public void TestExtractInterfacePass()
         }
 
         [Test]
-        public void TestCheckFlagEnumsPass()
+        public void TestCheckEnumsPass()
         {
             var @enum = AstContext.Enum("FlagEnum");
+            var enum2 = AstContext.Enum("FlagEnum2");
+            var boolClassEnum = AstContext.Enum("BoolEnum");
+            var ucharClassEnum = AstContext.Enum("UCharEnum");
+
             Assert.IsFalse(@enum.IsFlags);
+            Assert.IsFalse(enum2.IsFlags);
+            Assert.IsFalse(boolClassEnum.IsFlags);
+            Assert.IsFalse(ucharClassEnum.IsFlags);
 
-            var @enum2 = AstContext.Enum("FlagEnum2");
-            Assert.IsFalse(@enum2.IsFlags);
+            Assert.IsTrue(boolClassEnum.BuiltinType.Type == PrimitiveType.Bool);
+            Assert.IsTrue(ucharClassEnum.BuiltinType.Type == PrimitiveType.UChar);
 
-            passBuilder.AddPass(new CheckFlagEnumsPass());
+            passBuilder.AddPass(new CheckEnumsPass());
             passBuilder.RunPasses(pass => pass.VisitASTContext(AstContext));
 
             Assert.IsTrue(@enum.IsFlags);
-            Assert.IsFalse(@enum2.IsFlags);
+            Assert.IsFalse(enum2.IsFlags);
+            Assert.IsFalse(boolClassEnum.IsFlags);
+            Assert.IsTrue(ucharClassEnum.IsFlags);
+
+            Assert.IsTrue(boolClassEnum.BuiltinType.Type != PrimitiveType.Bool, "C# does not support Bool enums");
+            Assert.IsTrue(ucharClassEnum.BuiltinType.Type == PrimitiveType.UChar);
         }
 
         [Test]

src/Generator/Driver.cs

@@ -244,7 +244,7 @@ public void SetupPasses(ILibrary library)
             passes.AddPass(new FastDelegateToDelegatesPass());
             passes.AddPass(new FieldToPropertyPass());
             passes.AddPass(new CheckIgnoredDeclsPass());
-            passes.AddPass(new CheckFlagEnumsPass());
+            passes.AddPass(new CheckEnumsPass());
             passes.AddPass(new MakeProtectedNestedTypesPublicPass());
 
             if (Options.IsCSharpGenerator)

src/Generator/Passes/CheckEnumsPass.cs

@@ -0,0 +1,76 @@
+using CppSharp.AST;
+using CppSharp.Extensions;
+
+namespace CppSharp.Passes
+{
+    /// <summary>
+    /// Validates enumerations and checks if any should be treated as a collection
+    /// of flags (and annotate them with the .NET [Flags] when generated).
+    /// </summary>
+    public class CheckEnumsPass : TranslationUnitPass
+    {
+        public CheckEnumsPass()
+            => VisitOptions.ResetFlags(VisitFlags.NamespaceEnums);
+
+        private static bool IsFlagEnum(Enumeration @enum)
+        {
+            // If the enumeration only has power of two values, assume it's
+            // a flags enum.
+
+            var isFlags = true;
+            var hasBigRange = false;
+
+            foreach (var item in @enum.Items)
+            {
+                var value = item.Value;
+
+                if (value >= 4)
+                    hasBigRange = true;
+
+                if (value <= 1 || value.IsPowerOfTwo())
+                    continue;
+
+                isFlags = false;
+            }
+
+            // Only apply this heuristic if there are enough values to have a
+            // reasonable chance that it really is a bitfield.
+
+            return isFlags && hasBigRange;
+        }
+
+        private bool IsValidEnumBaseType(Enumeration @enum)
+        {
+            if (Options.IsCSharpGenerator)
+                return @enum.BuiltinType.Type.IsIntegerType();
+
+            return @enum.BuiltinType.Type.IsIntegerType() || @enum.BuiltinType.Type == PrimitiveType.Bool;
+        }
+
+        public override bool VisitEnumDecl(Enumeration @enum)
+        {
+            if (!base.VisitEnumDecl(@enum))
+                return false;
+
+            if (!IsValidEnumBaseType(@enum))
+            {
+                if (@enum.BuiltinType.Type == PrimitiveType.Bool)
+                {
+                    @enum.BuiltinType = new BuiltinType(PrimitiveType.UChar);
+                }
+                else
+                {
+                    Diagnostics.Warning(
+                        "The enum `{0}` has a base type of `{1}`, which is currently not supported. The base type will be ignored.",
+                        @enum, @enum.BuiltinType);
+                    @enum.BuiltinType = new BuiltinType(PrimitiveType.Int);
+                }
+            }
+
+            if (IsFlagEnum(@enum))
+                @enum.Modifiers |= Enumeration.EnumModifiers.Flags;
+            
+            return true;
+        }
+    }
+}

src/Generator/Passes/CheckFlagEnumsPass.cs

@@ -172,6 +172,7 @@ public void TestPrimitiveOutRefParameters()
         }
     }
 
+    [Test]
     public void TestPrimitiveInOutParameters()
     {
         using (var hello = new Hello())

tests/dotnet/Common/Common.Tests.cs

@@ -1,7 +1,7 @@
 #include "AST.h"
 #include <vector>
 
-// Tests class templates accross translation units
+// Tests class templates across translation units
 // Explicit instantiation
 template class TestTemplateClass<Math::Complex>;
 // Implicit instantiations

tests/dotnet/Native/ASTExtensions.h

@@ -14,6 +14,20 @@ enum FlagEnum2
   D1 = 1 << 4,
 };
 
+enum class BoolEnum : bool
+{
+    True = true,
+    False = false,
+};
+
+enum class UCharEnum : unsigned char
+{
+    A = 1 << 0,
+    B = 1 << 1,
+    C = 1 << 2,
+    D = 1 << 3,
+};
+
 class Foo
 {
     void toIgnore() { }